Answer:
He drove there at 60 mph, and he drove back at 36 mph.
Step-by-step explanation:
one way distance = d = 270 miles
average speed on way back = s
average speed on the way there = s + 24
time driving there = t
time driving back = 12 - t
average speed = distance/time
distance = speed * time
going there:
270 = (s + 24)t
270 = st + 24t
going back
270 = s(12 - t)
270 = 12s - st
We have a system of equations:
270 = st + 24t
270 = 12s - st
Solve the first equation for t.
t(s + 24) = 270
t = 270/(s + 24)
Substitute in the second equation.
270 = 12s - s[270/(s + 24)]
270 = 12s - 270s/(s + 24)
Multiply both sides by s + 24.
270s + 6480 = 12s^2 + 288s - 270s
12s^2 - 252s - 6480 = 0
Divide both sides by 12.
s^2 - 21s - 540 = 0
(s - 36)(s + 15) = 0
s = 36 or s = -15
The average speed cannot be negative, so we discard the solution s = -15.
s = 36
s + 24 = 60
Answer: He drove there at 60 mph, and he drove back at 36 mph.
Answer:
12-13
Step-by-step explanation:
the actual number is 12.64 whether your round up or down is up to you
Answer: c
hope this helps!
Answer:
The appropriate probability model for X is a Binomial distribution,
X 
Bin (<em>n</em> = 5, <em>p</em> = 1/33).
Step-by-step explanation:
The random variable <em>X</em> can be defined as the number of American births resulting in a defect.
The proportion of American births that result in a birth defect is approximately <em>p</em> = 1/33.
A random sample of <em>n</em> = 5 American births are selected.
It is assumed that the births are independent, i.e. a birth can be defective or not is independent of the other births.
In this experiment the success is defined as a defective birth.
The random variable <em>X</em> satisfies all criteria of a Binomial distribution.
The criteria are:
- Number of observations is constant
- Independent trials
- Each trial has only two outcomes: Success and Failure
- Same probability of success for each trial
Thus, the appropriate probability model for X is a Binomial distribution, Bin (<em>n</em> = 5, <em>p</em> = 1/33).
Answer:
<span>=3<span>√6</span>−3<span>√5</span></span>
Explanation:
<span>3<span><span>√5</span>+<span>√6</span></span></span>
We rationalise the denominator by multiplying the expression by the conjugate of the denominator. <span><span>√5</span>−<span>√6</span></span>
<span><span>3⋅<span>(<span>√5</span>−<span>√6</span>)</span></span><span><span>(<span>√5</span>+<span>√6</span>)</span>⋅<span>(<span>√5</span>−<span>√6</span>)</span></span></span>
<span>=<span><span>3⋅<span>(<span>√5</span>)</span>+3⋅<span>(−<span>√6</span>)</span></span><span><span>(<span>√5</span>+<span>√6</span>)</span>⋅<span>(<span>√5</span>−<span>√6</span>)</span></span></span></span>
<span>=<span><span>3<span>√5</span>−3<span>√6</span></span><span><span>(<span>√5</span>+<span>√6</span>)</span>⋅<span>(<span>√5</span>−<span>√6</span>)</span></span></span></span>
<span>Applying identity
<span><span>(a+b)</span><span>(a−b)</span>=<span>a2</span>−<span>b2</span></span> to the denominator.</span>
<span>=<span><span>3<span>√5</span>−3<span>√6</span></span><span><span><span>(<span>√5</span>)</span>2</span>−<span><span>(<span>√6</span>)</span>2</span></span></span></span>
<span>=<span><span>3<span>√5</span>−3<span>√6</span></span><span>5−6</span></span></span>
<span>=<span><span>3<span>√5</span>−3<span>√6</span></span><span>−1</span></span></span>
<span>=−3<span>√5</span>+3<span>√6</span></span>
<span>=3<span>√6</span>−3<span>√<span>5
</span></span></span>
